hastings



H. C. HASTINGS.

ELECTROMAGNETIC SWITCH.

APPLICATION FILED .IULYE, I919. I

Patented Feb. 17,1920.

2 SHEETS-SHEET 1 FISDDJ.

Inventor- Hammond C. Hastin H. c. HASTINGS. ELECTROMAGNETIC SWITCH,

APPLICAT ON FILED JULYB, I919. 1,331,063, Patented Feb. 17,1920.

2 SHEETS-SHEET 2.

D K B C 25 370/51)? and Com ensat/n 60/76.

urren I y P y inventor:

Hammond 0. Hastings,

His Att orney.

UNITED STATES PATENT OFFICE.

HAMMOND CHARLES HASTINGS, OF RUGBY, ENGLAND, ASSIGNOR TO GENERALELECTRIC COMPANY, CORPORATION OF NEW YORK,

' ELECTROMAGNETIC SWITCH.

To all whom it may concern:

Be it knownthat I, HAMMoNn CHARLES HA TINGS, a subject of Great Britain,residi the starting, of electric motors,- it has been the practice toemploy a plurality of lelectroma'g'netic 's witches, which closesuccessively to'cut out sections of resistance from the motorcircuitandbringthe motor up to speed... Various means have been devised forcontrolling the operation of the switches so that they will only closewhen the current is at a proper value, that is, afterla switch hasoperated to cut out a section of resistance the next switch will notoperate until the current has dropped to a safe value due to'thespeeding up ofthe motor. a

A form of switch which hasfrequently been proposed for this purpose isone in which a shunt coil closesthe switch and a: series coil, insteadof controlling theI-circuit of the shunt coil, positively prevents theswitch from closing by actually holding it open,.that is, the shunt coilpulls against the series, or holding-out coil. The diiiiculty with thistype ofswitch is that the value of current in the holding-out winding atwhich the switch will close depends upon the pull ofthe shunt coil,which of course will vary with the voltage and also with the temperatureof the coil. In other words, the-setting of the switch, z. e.. the motorcurrent value at which it closes. changes with change of voltage' Italso closes at one value of current in the series coil when the shuntcoil is cold and another when it is at its operating temperature whichis ordinarily about degrees C.

The object .of the present invention is to obtain a lock-out magneth'avinu a shunt closing coil and series lock-out coil in which thebalance between the closing and holding open forces will not be aiiectedby the varia- Specification of Letters Patent.

Application filed July 8, 1919. Serial No. 309,300.

will be free from the disadvantages inherent to the use of a commonmagnetic circuit for the series lock-out coil flux .and the look-outcomponent of the shunt coil flux.

Referring to the drawings, Figure 1 'is a plan view of a contactorembodying my inout magnet having coil 16 and core 17 and a compensatingmagnet having shunt coil 18 and core 19. Coil 18 is connected in serieswith the shunt closing'coil l0, and isused for neutralizing the etlectofthe variations in pull of the shunt closing magnet. The magneticcircuits of the three magnets are independent of each other. The lever13 which forms the armature for the closing coil is shown having aprojection 15 which forms the armature forthe magnets 16 and 18, butthree separate armatures could be 'used, provided that they were rigidlyfixed together. 7

p In Fig. 1 the contactor is shown in .the

.open position, the lever 13 resting against the stop 20 which is madeotnon-magnetic material. .26 is a base of insulating mate rial, 23 and24: contacts for carrying the main current, and 25 spring for producingwiping action between the contacts in a manner well known in the art. Itwill be seen that the pulls due to the compensating magnet 18 andlock-out magnet 16, are both opposed to the closing magnet 10. Theonlyforces acting on the moving arm oi. the contactor when in the-openposition are those due to gravity, lock-out magnet and compensatingmagnet tending to lock open. and the force due to the shunt coil 10tending to c ose the contractor. No springs are used. The compensatingandvlock-out magnets are both fitted with adjustable air gaps, so thatthe magnetic circuit of either can be altered without affecting themagnetic circuit of the shunt closing coil. The compensating magnetcircuit is adjusted in the first place to give the necessarvcompensating eflect-bv means of the adjustable iron cap 22. which isthen permanently locked in position [on the core 19. As the coil 18 ofthis magnet is eerie rit -tee an eee ea a l 0 the same changes incurrent, due to heating and voltage variation, occur in both coils. Themagnet circuit of 18 is proportioned so that any change in the pull oftheclosing magnet is balanced by a corresponding change of the pull dueto 18, over the workingsrafigeof the contacto'r. The cap 22 enablessmall adjustments to be made to compensate for variations inmanufacture; The adjustableiron cap 21 of the series lock-out magnetis'used for adjusting the reluctance I .of the magnetic pathof thismagnet, so that 'the lever l5'wfll be released and contactorsa'ting.magnet, assuming that this operates .at .the same leverage asthe closing coil.

Both are. showrron the same sideof the 1101i- .zo'ntaLa-Xis, althoughone is opposed to the jother. --.OB'=cur rei'1t corresponding to maxi-.mum line volts when, coil is cold.- OD:CUI' rent corresponding tominimum line volts ,lwhen .coil is 'atits maximum temperature.

AGzchange in the pull of the closing coil due .to maximum variation intemperature and line volts. AEIQlOSlIli force opposed to gravity and theseries 100 -out coi when shunt .coilcjurrent is OB. CF::closing forceopposed to gravity and the series lockeout coil when shunt coil currentis OD.

If forall'p oints such as K between D and B the corresponding closing.iorce HJ opposed to 'ravity and the-series-lock-out coil 1s sucht atHJzAEzCF exact compensation isproduced and the resultant closing Iforceopposed to gravity and the series lockout coil will be-constant for allvariations of current in the closing coil for the working range 'of thecontactor. This is the result which is required sothat when the lockoutmagnet is set to release at a particular valueof the'current, it willdo, so, although the current in the closingecoil may have any valuebetween OD and OB.

The advantages of my contactor over A thosejpreviou'sly devised will bereadily understood from the following :-If the magnetic circuit of thelock-out magnet were not independent of the magnetic circuit of theclosing-coil, the release current adjustment could not be made asdescribed above, as altering the reluctance of the series lock-outmagnet would at the same time affect the closin circuit and wouldtherefore not produce thedesired efi'ect. If as an alternative theadjustmentis not madeby altering the magnetic path, but by altering thetension of a spring applied so as to oppose the force of the lock-out'ni'agnet the "arrangement being such that the lock-out magnet has toattract its armature to it through an air gap'there is a possibility ofthe contactor closing while the current in the series coil is higherthan the desired value. The reason for this is that with such anarrangement a higherivalue of current is required in the series coil toattract the armature through the air gap, than to retain it in aposition closer to the coil. For the same reason, such an arrangementcannot be set so that a miniinumlock-out value of the current is asclose to the corresponding maximum value of the series current at whichthe contactor will close, as the contactor we have described in whichthe armature of the lock-out magnet when in the open position is broughtby gravi ty to the positlon where it is retained v by thelock-outmagnet.

In accordance with the provisions of the patent statutes, I havedescribed the principle of operation of my invention, together with theapparatus which I now consider to v represent thebest embodimentthereof, but

'I desire tohave it understood that the apparatus shown is onlyillustrative and that I the invention can be carried out by other posingmagnet drops to a predetermined value.

out typehaving a shunt wound closing magnet, a series lockout magnet theflux path of which is independent of that of the closing magnet, and ashunt wound compensating magnet the coil of which is in series with theclosing coil and the pull of which assists the look-out magnet, so thatvariations in pull of the closing magnet due to voltage and temperaturevariations are balanced by corresponding variations in the pull of thecompensating magnet. 1

.3. An electromagnetic switch having a single movable pivoted switchlever, a shunt wound closing magnet for actuating the switch, a serieslock-out magnet and a shunt wound compensating magnet the coil of whichis in series with the closing coil and the'pull of which assiststhe-lock-out magnet, the flux paths of the series lock-out magnet andthe shuntavound compensating magnet being independent of other 2. Anelectromagnetic switch of the lockand inde' pendent of that of theclosing magnet, whereby variations in the closing force due tovariations in the current in the shunt wound closing magnet are balancedby corresponding variations in the pull of the compensating magnet sothat the switch will be actuated when the current in the opposing magnetdrops to a predetermined value.

4. An electromagnet switch having a single movable pivoted switch lever,a shunt wound closing magnet on one side of the fulcrum of said lever, aseries lock-out magnet and a shunt wound compensating magnet the coil ofwhich is in series with the closing coil and the pull of which assiststhe lock-out magnet, on the other side of the fulcrum of said lever, theflux paths of the series lockout magnet and the shunt wound compensatingmagnet being independent of each other and independent of that of theclosing magnet, whereby variations in the closing force due tovariations in the current in the shunt Wound closing magnet are balancedby corresponding variations in the pull of the compensating magnet sothat the switch will be actuated when the current in the opposing magnetdrops to a predetermined value.

In witness whereof, I have hereunto set my hand this 13th day of June1919.

HAMMOND CHARLES HASTINGS.

Witnesses:

JOHN HALFORD, DOROTHY WHITE.

